The subject invention relates to electrical apparatus, such as transformers and capacitors, which include a liquid dielectric fluid and a porous construction in part. Such apparatus is characterized by the adsorbtion of the liquid into the pores of structual support media, thereby rendering difficulty in the complete removal of said liquid.
For many years Polychlorinated Biphenyls have been used as an insulation fluid in the electrical apparatus industry as a safe fire resistant material. In the late 60's and early 70's it was discovered that Polychlorinated Biphenyls were an environmetal contaminant and their use was discontinued, however, by that time many pieces of electrical apparatus had been built using the Polychlorinated Biphenyls as an insulation media.
A primary use of Polychlorinated Biphenyl is in electrical transformers and electrical capacitors. This invention is in relation to the clean up and removal of the Polychlorinated Biphenyls from the apparatus and the eventual reclassification of the apparatus as non-Polychlorinated Biphenyl equipment. For reclassification it is necessary that tests demonstrate a contamination of less than 50 ppm of Polychlorinated Biphenyl after three months of operation after the completion process.
The transformers which are contaminated with Polychlorinated Biphenyls all have a major similarity in that they contain the cellulosic material installation usually of a paper wrap on the wire, comprising the core of the transformer. Included in the transformer may be wooden structures acting as insulators. Because of these two major items, the transformer acts as a sponge and Polychlorinated Biphenyls are impregnated into these materials. They are contained in such a manner that a single wash will not remove them, and that over a period of time the Polychlorinated Biphenyls will leach out of the cellulosic material and come to an equilibrium level in the transformer even if it had been filled with clean non-Polychlorinated Biphenyl oil.
A similar problem is encountered in the disposal of transformers and capacitors which are impregnated with Polychlorinated Biphenyls or Polychlorinated Biphenyl contaminated liquids. Regulations imposed by the United States Environmental Protection Agency prohibit the recovery and recycling of the equipment and the materials contained therein unless the equipment can be certified as non-Polychlorinated Biphenyl under those regulations.
Several methods are used or have been proposed for the cleanup of transformers. There are complete flushings with several classes of fluid thereby generating large volumes of Polychlorinated Biphenyl contaminated or Polychlorinated Biphenyl material by U.S. Environmental Protection Agency definition.
The problem with prior methods is that they either generate a very large volume of contaminated fluid, with more than 500 ppm of Polychlorinated Biphenyl, or that they require long periods of time to successfully complete.